This invention relates to oil systems for turbines, and more particularly to filtering means for that oil.
A disadvantage of the oil strainer devices presently used for filtering return oil flowing from turbine drains is that the strainer cannot be removed for cleaning or inspecting during turbine operation without bypassing unfiltered oil to the turbine's reservoir. Bypassing oil directly from the turbine drains to the reservoir is undesirable because turbine lubrication oil and sealing oil is often supplied from that reservoir. If foreign contaminants happen to be present in the return oil which is bypassed when the filter has been removed for inspection or cleaning, those foreign contaminants will be supplied to the turbine bearings or seal rings causing serious harm to the seal rings, the bearings, and/or the turbine shaft. Damage to any one of the previously mentioned turbine parts can result in an extended turbine outage which can amount to .noteq.100,000 loss per day at typical cost figures. Additionally, the damage to turbine parts may be very expensive to repair. To reduce the chances of such a catastrophic occurrence, constant filtering of the turbine drains is necessary to prevent foreign contaminants from being carried back to the turbine reservoir. Multiple filters arranged in series on the return turbine oil drain lines were considered and judged to have increased maintenance requirements, higher production costs, inspection complications, and prohibitive retrofit costs for turbines already in operation. It was determined that any new filtering devices must continuously filter the turbine oil being returned to the reservoir during inspection and cleaning while being inexpensive to retrofit on existing turbine drain lines.